如何访问"fields_for“内部新建的实例？

<%= form_for @user do |f| %>
  <%= f.fields_for :profile do |profile_fields| %>
    <%= profile_fields.text_field :name %>
    <%= profile_fields.text_field :age %>
  <% end %>
  <%= f.submit %>
<% end %>

class UsersController < ApplicationController
  def new
    @user = User.new
    @user.build_profile # 创建关联的个人资料对象
  end

  def create
    @user = User.new(user_params)
    if @user.save
      # 保存用户及其关联的个人资料对象
    else
      # 处理保存失败的情况
    end
  end

  private

  def user_params
    params.require(:user).permit(:name, profile_attributes: [:name, :age])
  end
end